On 9/8/2015 8:20 PM, Stathis Papaioannou wrote:
On 9 September 2015 at 12:44, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote:On 9/09/2015 12:26 pm, Stathis Papaioannou wrote:On 9 September 2015 at 10:43, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote: On 9/09/2015 9:30 am, Stathis Papaioannou wrote:On 9 September 2015 at 09:23, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote: On 9/09/2015 8:56 am, Stathis Papaioannou wrote:On 8 September 2015 at 22:11, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote: On 8/09/2015 9:14 pm, Stathis Papaioannou wrote:On 8 September 2015 at 20:48, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote: On 8/09/2015 8:40 pm, Stathis Papaioannou wrote:On 8 September 2015 at 17:39, Bruce Kellett <bhkell...@optusnet.com.au <mailto:bhkell...@optusnet.com.au>> wrote: On 8/09/2015 4:56 pm, Stathis Papaioannou wrote:I will ask you the same question as I did Brent: do you conclude from the fact that when you toss a coin it comes up either as head or tails that the world does not split into two parallel versions of you, one of which sees heads and the other tails?I would conclude that a coin toss does not provide any evidence for multiple worlds or a split. The only evidence we have from this data is that the outcome of the toss is uncertain. There is no evidence there for any split of anything. It is not evidence FOR a split but is it evidence AGAINST a split?It is evidence that the assumption of a split is not necessary in order to understand everyday happenings. So, by the application of Occam's Razor, no split happens. So you agree that we would still observe the probabilities we do if we lived in a deterministic world in whaich all possibilities are realised?No, because not all possibilities happen in this world. If all possibilities were realized in this world, then there would be no uncertainty, no probabilities. Possibility and actuality would be the same thing. All the horses would win the Melbourne cup; and we don't live in such a world. Obviously, not all possibilities happen in this world, but they might happen in parallel worlds that don't interact with each other. The argument is that probabilities emerge from this, since you don't know which world you will find yourself in. You bet on the favourite in the race because you think you are more likely to end up in a world in which the favourite wins.In other words, probabilities can make perfect sense in a single deterministic world. This was understood a long time ago with the development of statistical mechanics. The idea that "all possibilities happen in parallel worlds" does not actually make a lot of sense. There is no current physical theory that implies this (without the addition of a lot of unevidenced assumptions). So probabilities do not emerge from this, they come from quite simple assumptions of randomness and ignorance. Probability in the MWI of quantum mechanics is problematic. Regardless of claims to be able to derive the Born Rule in Everettian models, all attempts fail because they are circular -- they need the Born rule in order to have non-interacting worlds, so you cannot then use these independent worlds to derive the Born rule. Gleason's theorem is no help -- it suffers from all the same problems as the Deutsch-Wallace approach. You don't seem to be disputing that we would still experience a probabilistic world even if all possibilities were actually realised, even though you do dispute that we in fact live in such a world. I'm not sure if you are disputing that, to give a simple model case, if a coin was tossed and the world split in two, with one version of you seeing heads and the other tails, the probability of each outcome is 1/2.Whether or not all possibilities are realized, they are not in evidence, so their relevance to the question of probabilities is questionable. Your simple model case of a coin toss causing a world split is just a made-up example to give the result you want, so again its relevance is dubious. There is no sensible physical theory in which the world splits on classical coin tosses. If you can't imagine a world split, consider a virtual reality in which the program forks every time a coin is tossed, one fork seeing heads and the other tails. You are an observer in this world and you have this information, so you know for certain that "all possibilities are realised" when the coin is tossed. What would you say about your expectation of seeing heads?I presume you mean that the world is duplicated on each toss, with one branch showing each outcome. We are back to the dreaded "person duplication" problem. My opinion on this is that on such a duplication, two new persons are created, so the probability that the original person will see either heads or tails is precisely zero, because that person no longer exists after the duplication.After the coin has been tossed a few times, you (or one of the entities identifying as you) will say that, despite the opinion he expressed on 9th September on the Everything List, it does seem that he has survived the duplication and that heads comes up about half the time.
But he would say the same thing if only one fork of the program were executed at each branch. So whether the other branches are executed is not related to observations.
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